Just as the law is that by which the right is enjoined, and by which sin is made manifest, so also the gospel is the promise of the grace and mercy of God, and therefore the forgiveness of sin and the testimony of God's benevolence toward us. Our minds assured of God's benevolence by this testimony believe that He has forgiven all guilt; and being this elevated, love and praise God and are exceedingly joyful and rejoice in God.... Moreover Christ is the pledge of all these promises; wherefore all scriptural promises must be referred to him, who at first obscurely, but later more clearly has been revealed in them.On the Meaning of the Gospel
And in the Apology of the Augsburg Confession
Since we obtain justification through a free promise, however, it follows that we cannot justify ourselves. Otherwise, why would a promise be necessary? The Gospel is, strictly speaking, the promise of forgiveness of sins and justification because of Christ. Since we can accept this promise only by faith, the Gospel proclaims the righteousness of faith in Christ, which the law does not teach. And this is not the righteousness of the law. For the law requires our own works and our own perfection. But to us, oppressed by sin and death, the promise freely offers reconciliation for Christ's sake, which we do not accept by works but by faith alone. This faith brings to God a trust not in our own merits, but only in the promise of mercy in Christ. Therefore, when a man believes that his sins are forgiven because of Christ and that God is reconciled and favorably disposed to him because of Christ, this personal faith obtains the forgiveness of sins and justifies us. In penitence and the terrors of conscience it consoles and encourages our hearts. Thus it regenerates us and brings us the Holy Spirit, so that we can finally obey God's law, love him and truly fear him, be sure that he hears us, and obey him in all afflictions. It mortifies our lust. By freely accepting the forgiveness of sins, faith sets against God's wrath not our merits of love, but Christ the mediator and propitiator. This faith is the true knowledge of Christ, it uses his blessings, it regenerates our hearts, it precedes our keeping of the law.Article IV On Justification